The present invention refers to a system for measuring the mass of fuel contained in a variable geometry container, and more specifically, to a system and method for measuring the mass of fuel contained in a portable container, particularly susceptible of being subject to external forces when it is embodied in an aircraft.
The measurement and indication to the crew of fuel quantity or fuel volume contained in a fuel container is a mandatory requirement in the aerospace field. Indeed, the fuel quantity present in the fuel container is a critical parameter that must be known at any time, as the fuel distribution in the aircraft affects directly, and in an important way, the distribution of center of gravity of the aircraft. Likewise, the remaining fuel is of major importance for managing the engine consumption and for Air-to-Air Refueling purposes, as being directly based on that parameter.
There are known several systems for measuring the mass of fuel within a container. In airplanes, the level gauge type sensors have been implemented for years. Such sensors are based on the measurement of the capacitance of a liquid, and although these systems are largely used nowadays, they are restricted to rigid containers only, as the volume and geometry of the container must be known at any time.
Alternatively to the level gauge type sensors, the use of load cell type systems is also known for fuel measurement purposes, also for being used in external containers embodied in an aircraft.
Regarding this, the document U.S. Pat. No. 5,133,212A discloses to determine the volume of a liquid contained in a tank submitted to external forces by means of one-axis load cells. However, the disclosure requires the fuel tank to only have one degree of freedom, being necessarily rigid in two of the three directions of the space. Therefore, the disclosure requires physically blocking the movement of the tank along two directions, entailing the need to fix it to the aircraft structure. Additionally, the document describes the need of a reference load cell to be used to determine the attitude of the aircraft.
Also, the document FR2976071A1 describes a system for measuring the liquid contained in a tank submitted to external forces by means of one-axis load cells. As the above mentioned document, the invention requires the use of gyroscopes and accelerometers to determine the attitude of the aircraft. Likewise, the French application requires the fuel tanks to be rigid-type tanks with one degree of freedom, newly, requiring physically blocking the movement of the tank along two directions and fixing it to the aircraft structure.
Thus, known systems for measuring the mass of fuel within a container requires the use of rigid-type containers with a unique degree of freedom, preferably along the yaw axis. This requirement entails the need to restrain or prevent movement in the two other directions, usually roll and pitch, which is not possible for a variable geometry container.
Therefore, there is a need in the aeronautical industry, for a new system and method which is capable of measuring the mass of fuel contained in a variable geometry container, also in the event that the container is non-rigid, such as a bladder, or the container is subjected to external forces when is in an aircraft.